Methods are known which provide for carrying out the preliminary preparation after diagnosis being established and decision made on radiation therapy application to the malignant neoplasm with the purpose of damaging its cells. In the course of preliminary preparation, linear dimensions, area and volume of pathological masses, organs and anatomic structures is determined and their positional relationship is described in quantitative terms for particular patient (see, for example: Radiation therapy of malignant tumors. Physician's handbook. Prof. E. S. Kiseleva, Ed., Moscow, “Meditsina” publishing house, 1996 [1], p.46-47). Principal task of the preliminary preparation lies in merging different data obtained in the course of the disease diagnosis and providing specialists effecting radiation treatment with topographic anatomical information on the site to be irradiated in the form allowing for development of irradiation program. In order to choose variants and parameters of irradiation program, it is necessary to know shape and dimensions of the malignant focus, its orientation in the body of patient, as well as relative position of surrounding organs and tissues, distance between the malignant focus and the most important in respect to radiation load distribution anatomical structures and critical organs. As a result of preliminary preparation and irradiation program development, in particular, specific points and areas are chosen on patient body surface, relative to which X-ray beams are oriented subsequently in the course of irradiation.
Principal disadvantage of the above combination of patient preparation to irradiation and irradiation proper lies in the fact of the stages being separated both in time and in space, in particular, due to that they are accomplished using different means. The irradiation (radiation treatment to damage the malignant neoplasm cells) is accomplished using directional sources of rather powerful X-ray radiation. As to roentgenoscopic investigation preceding the irradiation, it is made at substantially lower radiation intensities and, besides, constitutes usually only one of numerous methods used in combination: angiography, excretory urography, investigations of gastrointestinal tract, skeleton and cranial bones, and chest organs; radionuclide examinations of bones and liver; ultrasonic methods—echoscopy, echotomography, allowing visualization of abdominal cavity and pelvis organs and soft tissues; computerized tomography; magnetic resonance tomography, etc. As a consequence, it is extremely difficult to ensure high precision of radiation treatment, with the result of malignant focus tissues remaining partially unirradiated or intensive X-ray radiation being concentrated in the region exceeding the malignant focus in size. In the latter case, surrounding healthy tissues are damaged substantially stronger than at inevitable irradiation of healthy tissues located in the way of radiation to the malignant focus.
In realizing such technique, not only imprecision of the reference points selection and X-ray beams “aiming” during radiation treatment became manifest, but also variability of the internal organs location, and inaccuracy of patient accommodation during different seances of radiation treatment. Moreover, dose fractionation in itself, though caused by endeavor to avoid overirradiation of healthy tissues, results in vicious circle, because it is known that dose required for irreversible damage of the malignant focus, when applied in single exposure, is several times as less as the total dose required at fractionation [1, p.84, 91].
In a number of known technical solutions, special measures are taken to overcome this drawback, directed at exactness and stability enhancement of the patient positioning (see, for example, U.S. Pat. No. 5,983,424, publ. Nov. 16, 1999 [2]).
Another way to overcome said drawbacks lies in application of so called simulator—roentgenological apparatus similar in geometric and kinematical capabilities to the teleirradiation apparatus [1 p.55]. With simulator it is possible, without patient position changing, to “X-ray” him in different directions. During preliminary preparation patient is placed on the simulator table in a position, corresponding to that in which he will be during irradiation, and roentgenoscopy is performed. Using light crosshairs and relocatable roentgenocontrast threads, center and boundaries of irradiation volume are chosen, and plane is designated in which central axis of radiation beam will pass during radiation exposure.
However, none of such measures allow to avoid inaccuracies in the “aiming” of beams effecting radiation exposure on malignant neoplasm, caused by tumor growth. This factor turns out to be the most essential at lengthy treatment terms, when irradiation sessions are distanced in time from the moment of diagnostic examination of patient.
Technical solutions most close to the inventions proposed are disclosed in U.S. Pat. No. 5,207,223 (publ. May 4, 1993 [3]). In the methods (method of radiation exposure of malignant neoplasm and its constituent method of determination of refined location of malignant neoplasm) of this patent utilizing directed X-ray beams allowing to obtain images of patient tissues structure, such images are produced immediately before the radiation exposure and used in comparison with the results of previous diagnostic examinations to correct the irradiation program. At that, however, different beams are used for producing said images and for radiation treatment of malignant focus tissues, which allows not in principle to avoid mistakes in irradiating beams orientation.
Besides, operating principle of known methods and means is based on the use of information contained in shadow projections of tissues and organs through which X-ray radiation had passed. Therefore, information on the actual density of tissues and organs being of interest (in the given case—on density of tissues and organs in the presumable location of malignant focus) is distorted due to the presence of other tissues and organs in the way of “transmitting” radiation beam. At that, only high qualification of specialist carrying out the roentgenoscopy allows to differentiate image elements relating to malignant neoplasms. In case of projections overlapping of the neoplasm and some solid organs, unequivocal conclusion is difficult to make. It requires production of another image projection with different orientation of “transmitting” beam, which is associated with increase in irradiation dose. Effect of drawbacks of the group considered is diminished in the means realizing computed tomography principles, which entails not only complexity of corresponding technical means, but also rather high irradiation dose.